The present disclosure generally relates to methods and devices for detecting abnormal fluid flow through an infusion system. In particular, the present disclosure is related to devices and methods for detecting occlusions within an infusion system.
Liquid medicaments and other complex medical and therapeutic fluids are often administered to patients through infusion systems. A typical infusion system includes a fluid supply, an infusion flow control device and a fluid pathway. The infusion pathway typically includes one or more sections of fluid lines made of flexible tubing that define a fluid flow path from the fluid supply to a device that administers the fluid to the patient, such as a cannula, needle or catheter. During operation of the infusion system, the infusion control device pushes or forces liquid from the fluid source through the fluid pathway and the administering device into the patient.
One of the problems that can arise during infusion therapy is an occlusion or blockage which completely blocks or severely limits the flow of fluid through the infusions system. Occlusions are undesirable because they can impair the therapeutic effect of a medication being infused. For example, in some infusion therapy applications the liquid medicament is required to be delivered at a specific fluid flowrate for the medicament to be therapeutically effective. In these instances, an undetected occlusion, causing a decrease in flowrate, can diminish the therapeutic effect of the infusion therapy.
Additionally, in any infusion therapy application, an undetected occlusion can cause unnecessary delays in the infusion procedure. For instance, if an occlusion is undetected for a relatively long period of time, the time that passes while the occlusion is undetected increases the time required for the infusion therapy. Thus, in order to avoid complications and unnecessary delays in the infusion therapy, it is beneficial to be able to detect occlusions as soon as possible.
Because an occlusion causes pressure to build within the fluid lines, one common method of detecting an occlusion within an infusion system includes monitoring the pressure of the fluid lines and activating an alarm when the back pressure exceeds a preset threshold. In such methods, a pressure sensor is placed in communication with a fluid line of the system. When an occlusion occurs in the fluid line, flow within the line is blocked or severely limited. As more fluid is added to the fluid pathway by the flow control device, the pressure within the fluid line increases. When the pressure exceeds a certain threshold, an alarm is activated to inform the patient or operator of the occlusion.
In infusions therapies where the fluid flowrate is relatively high, an occlusion causes a fairly quick increase of pressure within the fluid line, and the occlusion can be detected by a pressure sensor in a relatively short period of time. However, in infusion therapies where the flowrate is relatively low (for example, between about 0.1 ml/hr and about 10 ml/hr), pressure build-up within the fluid lines due to an occlusion can take a significant amount of time to reach the threshold level required for activating the occlusion alarm. Thus, when pressure of the fluid lines is used to detect occlusions in infusion system having low flowrates, there can be a considerable delay between the actual occurrence of an occlusion and the detection of the occlusion.